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Enhanced femtosecond laser-plasma x-ray source utilizing microstructured liquid metal targetтезисы доклада
- Авторы: Ivanov K.A., Uryupina D.S., Volkov R.V., Savel’ev A.B., Brantov A.V., Bychenkov V.Yu, Paskhalov A.A., Eremin N.V.
- Сборник: Technical Program of Fourth International Conference on Superstrong Fields in Plasmas 2010
- Тезисы
- Год издания: 2010
- Место издания: Milan, Italy
- Аннотация: We have demonstrated, that manifold enhance of hard x-ray yield occurs at interaction of sub-relativistic laser pulse with microstructured by short prepulse surface of liquid metal target. Varying the energy of the prepulse it is possible to control the size of microstructures and hence the parameters of laser-plasma x-ray source. At the same time the use of liquid metal avoids the necessity of permanent target movement and permits to create a stable controllable source of short x-ray pulses operating at up to 1 kHz repetition rate. This source can find wide application in nanostructures investigation, x-ray spectroscopy with high temporal resolution, EXAFS spectroscopy, medical researches etc. In our experiments plasma was created by laser pulse delivered by 0.2 TW Ti:Sa laser system (pulse duration – 55 fs, wavelength – 800 nm, repetition rate – 10 Hz). Melted gallium at 300 oC was used at as a target. In stability research experiment we also have exploited another Ti:Sa laser system (pulse duration – 100 fs, wavelength – 800 nm, energy per pulse – 2 mJ, repetition rate – 100-1000 Hz). We showed that introduction of short prepulse with energy from 1 nJ to 0.1 mJ, outrunning the main laser pulse (~ 1-2 mJ in these experiments) over 12 ns nanoseconds, leads to formation of preplasma with uniform periodically structured jets emitted from dense part of cloud which strongly affect on x-ray yield. The size of these structures by the time of main pulse arrival is a few µm and depends on prepulse energy. At prepulse energy of 0.02 mJ (~50-1 of main pulse energy), which corresponds to ~7 µm diameter of jets, we achieved a 60 times increase in hard x-ray yield and almost fourfold growth of hot electron energy in plasma (from 20 keV to 75 keV at peak intensity 4x1016 W/cm2), comparing to plasma, formed by a pulse with smallest prepulse amplitude of 10-6. We also observed Ga Kα (9.3 keV) and Kβ (10.3 keV) line radiation from plasma, which intensities also increases at the same rate with prepulse energy growth. Furthermore parameters of plasma do not depend on laser pulse polarization. Numerical 3D PIC simulation of laser-plasma interaction revealed that when the laser pulse acts on structured surface of target (with few spindles few µm in diameter and 10-20 µm in length placed at the laser focus) prominent increase in the number and energy of fast electrons occurs in close agreement with experimental data. We also made simulation at much higher intensities showing applicability of our approach for generation of harder x-rays radiation and fast ions. We have also demonstrated that liquid gallium can be used as a stable laser-plasma source of x-ray pulse with repetition rate up to 1 kHz. Without additional focusing such source remains stable about 30 seconds, whereas with additional focusing – up to few hours of continuous work with almost 109 Kα photons/second.
- Добавил в систему: Иванов Константин Анатольевич